CANUCS/Technicolor: JWST medium-band photometry finds half of the star formation at z > 7.5 is obscured

Martis, Nicholas S. (author), Bradač, Maruša (author), Felicioni, Giordano (author), Harshan, Anishya (author), Judež, Jon (author), Markov, Vladan (author), Rihtaršič, Gregor (author), Tripodi, Roberta (author)

We present a sample of 110 high-redshift (z > 7.5) galaxies from the CANUCS and Technicolor surveys, showcasing photometry in every wide- and medium-band NIRCam filter in addition to ancillary Hubble Space Telescope data sampling 0.4–5 $\mu$m (22 JWST bands out of 29 bands total). Additionally, 47 (43%) galaxies in our sample meet criteria to be classified as extreme emission line galaxies, 17 (15%) of which are completely missed by typical dropout selections due to faint ultraviolet (UV) emission. By fitting the spectral energy distributions covering the rest-frame UV to optical at z > 7.5, we investigate the dust obscuration properties, giving an unbiased view of dust buildup in high-redshift galaxies free from spectroscopic follow-up selection effects. Dust attenuation correlates with stellar mass, but more strongly with star formation rate. We find typical galaxies at z > 7.5 have ∼25% of their star formation obscured. However, since galaxies with higher star formation rates suffer more attenuation, ∼50% of the total star formation rate density at 7.5 < z < 9 is obscured. The obscured fraction drops to ∼25% in our 9 < z < 12 bin, possibly due to substantial dust grain growth in the interstellar medium not having time to occur. Extrapolating the decline in dust obscuration of galaxies to higher redshifts, we infer that dust obscuration should approach zero at z > 15, implying that epoch as when dust first forms in bright galaxies.

• Language: English
• Keywords: astrophysics, high-redshift galaxies, interstellar dust, photometry
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 12 str.
• Numbering: Vol. 990, no. 1, art. no. 83
• PID: 20.500.12556/RUL-176607
• UDC: 524.5
• ISSN on article: 1538-4357
• DOI: 10.3847/1538-4357/adf32a
• COBISS.SI-ID: 260112387
• Publication date in RUL: 05.12.2025

Record is a part of a journal

• Title: The Astrophysical journal
• Shortened title: Astrophys. j.
• Publisher: University of Chicago Press for the American Astronomical Society
• ISSN: 1538-4357
• COBISS.SI-ID: 515079705

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: astrofizika, galaksije z velikim rdečim premikom, medzvezdni prah, fotometrija